New Januscape Linux flaw allows VM escape on Intel, AMD devices

A long-standing Linux kernel issue dubbed Januscape allows attackers inside a guest virtual machine to escape into the host, leading to arbitrary code execution or host crashes. The problem, tracked as CVE-2026-53359, is a use-after-free bug in KVM/x86 shadow MMU emulation and has been present for about 16 years before a June 2026 fix (commit 81ccda30b4e8). This matters for multi-tenant cloud environments running KVM, where exploitation can compromise other guests or cause denial of service.